November 22, 2016 02:04 PM UTC

The Square Root of Gerrymandering

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• by: Colorado Pols

Michael Wines of the New York Times has a fascinating look at a new court ruling in Wisconsin that has the potential to dramatically change the process of redistricting/reapportionment across the country.

A panel of three federal judges ruled on Monday that the Wisconsin legislature relied upon unconstitutional partisan gerrymandering when it redrew state legislative districts in 2011.  The case could now move to the Supreme Court, where a new mathematical formula designed to measure partisan gerrymandering could significantly alter the next round of state redistricting/reapportionment in 2021. From the Times:

In Monday’s ruling, the court was swayed by a new and simple mathematical formula to measure the extent of partisan gerrymandering, called the efficiency gap. The formula divides the difference between the two parties’ “wasted votes” — votes beyond those needed by a winning side, and votes cast by a losing side — by the total number of votes cast. [Pols emphasis] When both parties waste the same number of votes, the result is zero — an ideal solution. But as a winning party wastes fewer and fewer votes than its opponent, its score rises.

A truly efficient gerrymander spreads a winning party’s votes so evenly over districts that very few votes are wasted. A review of four decades of state redistricting plans concluded that any party with an efficiency gap of 7 percent or more was likely to keep its majority during the 10 years before new districts were drawn.

In Wisconsin, experts testified, Republicans scored an efficiency gap rating of 11.69 percent to 13 percent in the first election after the maps were redrawn in 2011.

Some experts said the efficiency gap gives gerrymandering opponents their most promising chance yet to persuade a majority of the Supreme Court to limit partisan redistricting. [Pols emphasis]

The once-per-decade redistricting/reapportionment process is often a long, drawn-out (pun intended) process that involves months of legal wrangling from both sides of the political aisle. When it is done particularly poorly, as it was in the infamous 2003 “Midnight Gerrymandering” by Colorado Republicans, it can create deep political wounds that resonate for several election cycles.

We aren’t well-versed enough in election law to definitively say whether or not this “efficiency gap” calculation is the ideal approach for Colorado, but it would certainly be helpful if there were some sort of basic formula that every state could use when it begins the next redistricting/reapportionment process.